This document concerns an invention relating generally to vacuum chambers, and more specifically to vacuum chambers wherein items are to be subjected to testing, analysis, and/or imaging.
When performing operations on objects situated within ultra-high vacuum chambers (UHV chambers), it is often useful to be able to obtain images of the shape and position of the objects. As an example, in the case of an atom probe microscope having a local extraction electrode situated within a UHV chamber, the specimen to be analyzedxe2x80x94which is often provided in the form of a sharp tipxe2x80x94is best analyzed if it is precisely aligned within the aperture of the local electrode (which is generally 1-1000 micrometers in diameter). It is additionally useful to be able to view the specimen""s shape and status as experiments are performed.
However, obtaining a suitable view of the specimen with an optical microscope, digital camera, and/or other imaging device can be difficult to achieve. The UHV chambers, which must necessarily have sturdy construction, are generally made of metal with one or more access ports provided over a small area of the chamber walls, with the specimens being centrally located within the chambers to allow greater room to operate on the specimens. The access ports provide limited ability to view the specimen and ascertain its position and status; their distance from the specimen is such that it is difficult to view details of the specimen (even if high-powered optics are used), and additionally they each provide a very limited cone of vision about the specimen (i.e., one may generally see only one primary face of the specimen and very limited views of the sides of the specimen located off of the primary face). It is therefore generally unsatisfactory to optically image a specimen from an access port, since it is extremely difficult to obtain a view of the specimen having resolution in the ideal range (from 10 micrometers down to the sub-micrometer level), and to obtain sufficient views from points orbiting the specimen that one may effectively obtain more than a two-dimensional view of the specimen. As a result, optical imaging devices are generally only employed to obtain very coarse information regarding the position and status of the specimen.
Owing to the foregoing problems, specimen position/status information is often provided by use of indirect measurements. As an example, in the case of atom probe microscopes, measurements of transmitted or backscattered current (as discussed in U.S. Pat. No. 5,440,124 to Kelly et al.), or of the desorption rate of ions from the specimen (U.S. Pat. No. 5,061,850 to Kelly et al.), can indicate specimen location and orientation. However, these methods are only useful if the specimen is already aligned to some degree within the aperture of the microscope. Therefore, imaging is usually performed with use of scanning electron microscopes (SEMs) situated inside the chambers, since these can obtain submicron resolution of specimen position and status from relatively long working distances (i.e., with greater spacing between the SEM and the specimen).
However, while this well-accepted arrangement provides good information, it too is less than ideal. Initially, it is expensive to provide and maintain a SEM. Additionally, in order to establish high vacuum within UHV chambers, the chambers must undergo a heating or xe2x80x9cbakingxe2x80x9d process in order to drive off volatile molecules each time the chamber is opened to the atmosphere. SEMs have components that cannot withstand baking, and therefore portions of the SEMs must be removed prior to each bake cycle and then replaced after the bake cycle is complete. Since SEM components are sensitive and bulky, removal and replacement of SEM components is inconvenient and time-consuming. It would therefore be extremely useful to be able to obtain images of areas within the chambers which have suitable resolution and angular spread without having to resort to use of a SEM.
The invention involves a vacuum chamber which is intended to at least partially solve the aforementioned problems. To give the reader a basic understanding of some of the advantageous features of the invention, following is a brief summary of preferred versions of the vacuum chamber. As this is merely a summary, it should be understood that more details regarding the preferred versions may be found in the Detailed Description set forth elsewhere in this document. The claims set forth at the end of this document then define the various versions of the invention in which exclusive rights are secured.
A vacuum chamber includes chamber walls separating a chamber interior and a chamber exterior, with one or more access ports defined in the chamber walls. A viewing tube having a flange removably affixed to an access port provides a passage extending into the chamber interior and terminating in an at least partially transparent window. The viewing tube may therefore be installed on a vacuum chamber port by removing any standard cap situated on the access port, and inserting and affixing the viewing tube in place of the cap.
A positioner for imaging devices is then provided within the viewing tube, and is thus situated at least partially within the chamber interior with its imaging device(s) oriented towards the window of the viewing tube to allow imaging of areas within the vacuum chamber. A preferred version of the imaging device positioner includes an arcuate track which has a center of curvature situated within the vacuum chamber interior and which is fixed with respect to the access port, with a positioner carriage being movable along the track. The positioner carriage preferably bears wheels engaging opposing sides of the track, as well as a pinion which engages teeth on the track and which may therefore be actuated to drive the carriage along the track. A positioner subcarriage which bears an imaging device is then movably affixed to the positioner carriage, preferably so that it may be repositioned in a first plane oriented at least substantially perpendicular to the carriage plane and a second plane oriented at least substantially parallel to the carriage plane. The positioner subcarriage may be made repositionable with respect to the positioner carriage by extending one or more threaded members therebetween so that rotation of the threaded member(s) drives the positioner subcarriage with respect to the positioner carriage.
With the viewing tube and imaging device positioner installed, a user may use the imaging device positioner to reorient an imaging device within the viewing tube (and thus within the vacuum chamber interior) to very precisely direct it towards an area of interest within the chamber. Since the imaging device may be situated within the chamber interior very close to the area of interest for imaging and may be repositioned therein, the imaging device may obtain views of the area of interest within a greater viewing cone (i.e., along lines of sight separated by greater angles) than the imaging device would otherwise be able to achieve were it situated outside the vacuum chamber. Additionally, since the viewing tube rests along the same line of sight that the imaging device would require were it situated outside the vacuum chamber, the viewing tube does not unnecessarily occupy or obstruct valuable space within the chamber interior (since such line of sight must necessarily remain unobstructed in any event if the imaging device is to view the area of interest).